WO2001016043A1

WO2001016043A1 - Phosphostannate or borostannate pyrolitic coating, and glazing comprising same

Info

Publication number: WO2001016043A1
Application number: PCT/EP2000/008844
Authority: WO
Inventors: Eric Tixhon; Alain Schutz
Original assignee: Glaverbel
Priority date: 1999-09-01
Filing date: 2000-08-31
Publication date: 2001-03-08
Also published as: EP1218305A1; JP2003508326A; PL354407A1; CZ2002781A3; LU90432B1; AU1270801A

Abstract

The invention concerns glass panes comprising interferential assemblies of thin layers. The inventive glass panes comprise a glass substrate coated with a phosphostannate or borostannate layer, with a phosphorus or boron content not less than 6 %, the layer being deposited by pyrolysis. The phosphostannate or borostannate layers are particularly useful as an undercoat, for attenuating colours reflected by a layer providing the glazing with low-emissive, solar protecting or antiglare properties.

Description

Phosphostannate or borostannate pyrolytic layer, and glazing comprising this layer

The invention relates to layers deposited on transparent substrates, in particular glass, and which are part of an interference set of thin layers. In general, the invention relates to layers, and sets of layers, in which the former are integrated because of their characteristics, in particular of index, but also of transparency, of resistance, etc., in order to improve their characteristics.

In the following, more specific reference is made to the sublayers of such assemblies, sublayers which have the function in particular of modifying the color in reflection, induced on the glazing by the presence of these assemblies. These are, in particular, sets of thin layers which give transparent substrates low-emissivity, sun protection or anti-reflection properties. It is indeed about these properties that these sublayers have been most studied and developed. This is not exclusive of other uses.

A known difficulty, linked to the presence of these sets of layers, is the appearance of interference phenomena which, at the usual thicknesses, are manifested in particular in the form of parasitic colorations. These colors are all the more undesirable as the glass concerned is clearer. To make these parasitic colors disappear, or at least attenuate them to an acceptable level, it is known to interpose between the glass and the low-emissivity or anti-sun layer, or the set of anti-reflective layers, a transparent under-layer. well defined index and thickness. The theory makes it possible to precisely determine the appropriate values for these parameters. The practice however encounters some difficulties in the implementation due to the multiple technical constraints to which the industrial production of such layers must respond.

Among the most significant constraints, some are linked to the composition of the layers, others to the precursors used, others still, to the means used for their production.

In the latter category, mention should be made of the need to operate efficiently and economically. Pyrolysis is the preferred mode. It has the advantage of quickly leading to thick layers suitable, which moreover offer good homogeneity and good resistance, in particular mechanical, but also chemical. Among the pyrolysis techniques, gas phase pyrolysis, or CVD, is often the one that is most suitable when it can be practiced directly on the production line of a glass ribbon.

The choice of precursors is delicate. They must be inexpensive, obviously lead to the desired layers, but still offer sufficient reactivity, not be toxic, etc.

The choice of an underlay depends first of all on its performance. For this it is known that the sub-layer must have an index located between that of the glass substrate and that of the low-emissive, anti-sun or anti-reflective layer. As an indication, in the case of a glass sheet of the most usual soda-lime type, and of a low-emissive functional layer of tin oxide, the under-layer must have an index situated between approximately 1 , 5 and 1.9.

Still in the case of low-emissive layers based on tin oxide, to achieve these intermediate indices, the solution most frequently proposed in the literature consists in forming a mixed layer of silicon oxide, Si0 ₂ , and tin oxide, Sn0 ₂ . It has been proposed in particular to form layers of index varying gradually from that of glass to that of the low-emissivity or sunscreen layer. In the example of a layer of tin oxide, considered as a reference, this leads for example to deposit practically pure silica in contact with the glass, and to increase the content of tin oxide until there is tin oxide alone in contact with the upper layer.

The production of mixed oxide layers poses various problems. One of these lies in the means to be used to form the deposit properly, in particular when a gradient must be obtained. It is proposed, for example, to play on the difference in reactivity of the silica precursors and of the associated oxide. US Patent 5,356,718 is in this sense. Other solutions consist in arranging the pyrolysis installation so that the substrate is exposed successively to compositions in which the proportions of the precursors vary.

The practice of producing these layers, however, faces some difficulties. Obtaining mixed layers raises in particular questions of reproducibility which are not perfectly mastered. For this reason the use of multiple layers of step indices has been proposed to replace the index gradient layer. This is for example the purpose of US Patent 5,395,698. According to this patent, at least two layers of different indices are deposited successively. The first layer has the intermediate index closest to that of glass, the second layer has an index close to that of the low-emissivity or sunscreen layer with which it is in contact.

Regarding the formation of these mixed oxide layers, a difficulty highlighted in the literature is the low reactivity of the Si0 ₂ precursors which can be used in particular in CVD techniques. To improve the yield of pyrolysis, various solutions have been proposed, and in particular the use of so-called "accelerating" products. These products are added to the silica precursors and brought into contact with the surface to be coated.

The above shows a certain difficulty in controlling the production of this type of layer under industrial conditions of implementation. The invention proposes to provide a layer and the means for obtaining it, which guarantee satisfactory results, under easily achievable and well reproducible conditions.

The inventors have shown that a layer meeting these objectives can be obtained without having to use a mixed silica oxide, in other words, without forming a layer which by its composition constitutes a transition between the glass and the functional layer which is superposed on it. .

According to the invention, the layer consists of a phosphate or a tin borate.

The composition of the sublayers according to the invention is remarkable in particular, by the fact that it does not contain silica. Glazing with a layer containing phosphorus can be found in the literature. This element is then used as a "dopant" for the basic constituent oxides of these layers. Compared to these doped layers, regardless of the difference in function, the layers according to the invention are distinguished by their phosphorus content. For doped layers, phosphorus is in very small proportion compared to the other constituents. In practice, this element only enters the layer for a content which does not exceed 4 atomic%, and most often is of the order of 1 to 1.5%.

According to the invention, phosphorus or boron are constitutive elements of the structure of the layer, and, consequently, they are present in substantially greater proportions. According to the invention, the atomic phosphorus or boron content is not less than 6%, and most often is more than 10%. The layers according to the invention have an essentially amorphous structure.

The inventors have shown that it is possible to modulate the refractive index of the layers formed by varying their phosphorus or boron content. For the layers according to the invention the index is a function of the ratio

Sn / P (or Sn / B). To lead to the most useful indices, in particular for the attenuation of parasitic colorations coming from the low-emissive, anti-solar or anti-reflective layers, namely indices between approximately 1.6 and 1.8, the Sn / P (or Sn / B) is advantageously between 1 and 4, and preferably between 1.5 and 2.5. Similarly, in the case of the use of a sublayer according to the invention to attenuate the parasitic colorations produced by a typical low-emissive layer based on tin oxide (possibly doped), the index is around 1.9, particularly useful index values are around 1.7, in a range for example from 1.65 to 1.75, the Sn / P (or Sn / B) ratio is then advantageously from 1.85 to 2.25.

In general, the layers according to the invention advantageously have a refractive index of between 1.6 and 1.9.

Deposited on substrates made of soda-lime glasses, the layers according to the invention are of the Sn _x P _y O _z Na _w and S ^ B _y C ^ Na _{^ type.} In these formulas,, x, y and z represent the proportions respective atomic constituents.

The conditions making it possible to arrive at the preferred indices can also be expressed directly in terms of atomic proportions of the elements constituting the layers according to the invention. These proportions are advantageously:

- Sn 15 to 35%

- P (B) 6 to 20% the other constituents in this case are usually in proportions: - O 42 to 58%

- Na 6 at 23%.

In a particularly preferred manner, the constituent elements are in the following proportions:

- Sn 18 to 26% - P (B) 9 to 13% and the other elements in the proportions:

- O 48 to 52%

- Na 14 to 20%. Given the indices and thicknesses of the layers or sets of layers whose effects they correct, the layers according to the invention advantageously have a thickness of between 50 and 110 nanometers, and preferably between 60 and 100 nanometers. The phosphorus or boron precursors used to produce these layers by pyrolysis techniques, and in particular by gas phase pyrolysis, advantageously correspond to the following general formulas: (RO) ₃ P and (RO) ₃ B, in which R is an alkyl or alkenyl radical containing from 1 to 6 carbons.

Preferred precursors are triethylphosphite (TEP) and triethylborate (TEB), respectively.

For the formation of the layers according to the invention, the tin precursor is advantageously used monobutyltrichloretain (MBTC), tetramethyltin (TME), tin tetrachloride, tin ethylhexanoate. MBTC is preferred because it reacts properly at temperatures useful for pyrolysis, in particular in CVD on a production line for "float" glass. The reaction is neither too slow, which would lead to deposits that are difficult to produce, nor too rapid, which would have the counterpart of seeing it develop before contact with the glass, resulting in fouling of the apparatus and contamination of the layer by dust.

The pyrolysis reaction is advantageously carried out in the presence of a small amount of water. The influence of water manifests itself even in small proportions. This shows that water is not involved as the main source of oxygen in the formation of the layer. Without the reaction mechanism having been analyzed, it is reasonable to think that water first acts as a catalyst for the reaction. In the absence of water, the reaction is extremely slow to the point of not allowing production which can be used under industrial conditions.

Water can be replaced by compounds containing hydroxyl groups, or which are capable of leading to such groups under the conditions of pyrolysis. As an indication, the low molecular weight organic alcohols and acids such as acetic acid, ethanol, or the corresponding esters such as ethyl acetate can be used.

Variations in water concentration affect the reaction rate. This content is deliberately limited to avoid reactions which could develop in the gas phase to the detriment of the formation. of the pyrolytic layer. Advantageously, in the gaseous form, based on the tin precursor used, the water does not constitute more than 10% by volume. Preferably, still in the gaseous form, the water content is 3 to 7% by volume, based on the volume of the tin precursor. With the precursors, it is also possible to introduce a certain proportion of air, in particular in gas pyrolysis techniques. The reaction can be carried out in the complete absence of air, as indicated in the examples. This way of proceeding can be chosen in the case where the formation of the layer must imperatively take place in a non-oxidizing environment. If this condition is not required, it is advantageous to have a certain amount of air with the precursors to improve the reactivity.

In CVD techniques, contrary to what is observed with water, the air content is advantageously of the order of magnitude of that of the other precursors, or even in a proportion much higher than the stoichiometric proportions leading to the formation phospho- or borostannate.

The air introduced as a source of oxygen can be replaced, in part or in whole, by other compounds known to fulfill this role in pyrolysis techniques. Compounds likely to replace air are for example C0 ₂ or N ₂ 0.

The pyrolysis temperature is advantageously chosen so that the reaction is carried out directly on a production line for flat glass. In the most favorable conditions, namely at the exit from the enclosure of the "float", before the glass enters the drying rack, or even inside the enclosure, subject to the precautions necessary for preserving the atmosphere against possible contamination by the air used with the precursors, the preferred temperatures are between 550 and 670 ° C.

The invention is described in detail in the following examples carried out on an industrial production line. The deposition of sublayers is carried out by gas phase pyrolysis on the glass ribbon leaving the "float" tank, between the latter and the drying rack. The glass here has a temperature of 610 ° C.

The layer is formed from monobutyltin trichloride (MBTC) as a tin precursor, and triethylphosphite (TEP). The precursors are carried by nitrogen as a carrier gas. With MBTC a small amount of water vapor is introduced (3% by volume of the amount of MBTC).

By construction of the installation, and taking into account the speed of glass scrolling, the contact time of the glass with the precursors is 5 seconds for all the tests.

In these tests, air in variable quantities is also introduced with the precursors. The influence of the precursor contents on the deposition rate and on the index of the layer formed, in other words on its composition, is established. The quality of the layer is further specified by measuring the "haze". This is the measurement of the fraction of light scattered through the layer (ASTM 1003-61 standard). The flow rates of the precursors are expressed in liters per minute, those of nitrogen and air in standard cubic meters per hour (Nm ³ / h), the thicknesses in nanometers and the deposition rate in nanometers per second.

This table shows in particular that the increase in the amount of TEP in the gas flow (examples 5 to 8), the other conditions being maintained, has the consequence of increasing the deposition rate. From 9 nm / s the speed goes to 14.6 nm / s by doubling the PET flow. Under the same conditions, it can be seen that the refractive index of the formed layer decreases from 1.77 to 1.68.

These observations show that an undercoat of suitable index for attenuating the parasitic colorations produced by a low-emissive layer can be obtained with a suitable thickness under industrial conditions. In addition, the layers formed are of good transparency. Their absorption is less than 3% of the incident light. Furthermore, the presence of the layer is not accompanied by the formation of an annoying veil. The measured value of this veil ("haze") remains very low, and in all cases much less than the limit which is set at 0.6% for the sheet glass coated with the layer. In the formation of this value, the layer alone must not intervene for more than 0.4%.

Examples 1 to 4, for which the only parameter which is modified is the air content, show that the deposition rate increases with this content, but that this does not seem to have a significant influence on the value of the index of refraction. After a certain threshold, the increase in air flow no longer has any influence on the deposition rate.

The deposition rate also seems sensitive to the concentration of precursors (examples 1 to 4 compared to examples 5 to 8). For this reason, in a second series of tests on an industrial installation, the nitrogen flow is reduced. The conditions and results of these tests are given in the following table. As before, the processing time is 5 seconds.

The deposition rate is significantly increased due to the reduction in the carrier gas flow rate.

The refractive index decreases with the MBTC / TEP ratio. This clearly indicates that the phosphorus content in the layer makes it possible to control the refractive index independently, to a certain extent, of the deposition rate.

As before, this series of deposits shows the industrial feasibility of suitable layers. The index, the deposition rate and the optical quality of the layer meet the required conditions.

Additional tests are carried out in the laboratory to confirm the previous results and explore the influences of various parameters, and in particular of the water content in the precursors, as well as that of oxygen.

The results of these tests are shown in the following table. The nitrogen flow is constant at 15 liters per minute. The flow rates of MBTC and TEP are in milliliters per minute, that of O _z , which replaces air, is in liters per minute. The deposit time is in seconds. The water content is expressed in volume% relative to the MBTC.

Examples 19 and 22, for which phosphite is not introduced into the precursors, lead to tin oxide layers of index 1.9.

Examples 23, 24, 25 and 26 are distinguished from each other only by the concentration of TEP introduced. They show very clearly on the one hand, that the speed of formation of the layer increases with the concentration of TEP, and on the other hand, that at the same time, the refractive index of the formed layer decreases in a way very sensitive. Function of this last remark, and taking into account the fact that the intermediate indices for attenuating the iridescence of the most common solar or low-emissivity layers are around 1.7, the useful concentration of PET, and consequently the speed of deposit cannot be increased without further consideration. An increase in the TEP content beyond a certain threshold, even if it makes it possible to further increase the deposition rate, would indeed lead to an even lower index. This downward trend in the index can, however, be combated by simultaneously increasing the content of PET and MBTC. Test 18 thus simultaneously shows a particularly high deposit rate, and an index which is in the most useful range. It should be noted, however, that the increase in the deposition rate obtained in this example is not proportional to that of the quantities of precursors used. In all cases, it is therefore necessary to determine the best compromise between reactivity and efficiency of the operation.

The influence of the water concentration can be seen from Examples 17, 21 and 24. The deposition rate is apparently the element most sensitive to variations in the water content introduced with the precursors. The increase in the water content results in a higher reactivity.

A certain number of the layers formed on soda-lime glass was the subject of a quantitative determination of the constituent elements. The results are reported in the following table. The values indicated are the atomic percentages of the various constituents. For the record, the refractive indices of the layers also appear in this table.

On the quantitative determinations, we first observe the absence of carbon (less than 1%) which reflects a well executed pyrolysis. Of course, the layers do not contain silica.

The formation of the layer is systematically accompanied by the incorporation of sodium in a significant proportion. The origin is necessarily a diffusion from the surface of the glass. Unlike other layers deposited under similar conditions, the presence of sodium does not seem to generate a particular brittleness of these layers when they are covered by the low-emissivity or anti-reflective layer.

It can also be seen in this table that the refractive index of the layer is clearly dependent on the Sn / P ratio and evolves in the same direction. The more phosphorus in the layer, the lower the index and vice versa.

The layers according to the invention are advantageously used as a sublayer in glazing whose low-emissivity or sunscreen layer is an oxide layer of the tin oxide, indium oxide etc. type. These oxides, according to practice in this field, are also advantageously doped. Tin oxide can thus be doped with fluorine and indium oxide can be doped with tin. It may also be a layer of tin containing antimony according to the teaching of publications BE-A 1 010 321 and 1 010 322.

For glazing comprising a layer of tin containing antimony, the atomic proportion Sb / Sn is advantageously between 0.02 and 0.15, and preferably between 0.05 and 0.12%. The deposition of the functional layer is advantageously also carried out by a gas pyrolysis technique. In this case, it is preferred to have the deposition of the sublayer immediately followed by that of the functional layer. When the sublayer is produced in the enclosure of the "float", the deposition of the layer can immediately follow, either in the enclosure of the "float" or at the exit of this one. The temperature and environmental conditions allow these two methods.

Tests for the production of assemblies have been undertaken in which a sublayer of tin phosphostannate is covered with a layer of tin oxide containing antimony. The sublayer and the layer are deposited by gas pyrolysis. Systematically the layer of tin oxide containing antimony contains 10% antimony and has a thickness of 320 nanometers.

The sublayers are established for a series of thicknesses and for two types of composition corresponding respectively to the refractive indices 1.7 and 1.67. The atomic proportions of phosphorus in these sublayers are respectively 11.2 and 12.1%.

On the samples prepared, the colorimetric characteristics in reflection are determined. The measurements made are made according to R.S.

Hunter (Food Technology, Vol. 21, pages 100-105, 1967, and The Measurement of Appearance, Wiley and Sons, New York, 1975). The colorimetric measurements are expressed by two indices a and b. The more these indices are close to 0, the more the reflected light is neutral, in other words, the less it appears "colored". Furthermore, if a slight coloring cannot be avoided, the users prefer blue or green shades which correspond to negative values of a and, preferably, also to negative values of b. The coloring is also sometimes expressed in the literature by a third value, ç, defined by the relation: c = (a ² + b ² ) ¹²

For a glass to be considered as neutral in reflection, it has been proposed in US Pat. No. 4,206,252, that the value of ç remains less than 12, and preferably less than 8.

To ensure the absence of iridescence in reflection, the measurement of the indices a_and b is made for different incidences compared to the normal to the surface of the glass sheet. It is in fact the variations in coloring depending on the incidence which are at the origin of the undesirable iridescence.

The results of the measurements are collated in the following table. In this table the thicknesses are expressed in nanometers. Test 30 corresponds to the reference sample. This sample consists of a sheet of clear soda-lime glass on which the layer of tin oxide containing the antimony is deposited without an undercoat. Observation from all angles shows a relatively high index value ç. Under 40 and 50 °, the index is even higher than the limit value of 12. The reference sample, even according to the least severe criteria, is not neutral in reflection.

The other tests are all carried out by superimposing a sublayer according to the invention and the layer serving as a reference, on the same clear soda-lime glass. The sublayers were chosen to present indices halfway between the index of the glass sheet and that of the tin oxide layer containing the antimony.

Test 34 shows the importance of the thickness of the undercoat for obtaining the color attenuation. The thickness of 110 nanometers corresponds to the preferred upper value indicated for correcting undesirable reflection colorations for the typical structure chosen. At this thickness, the highest values of ç (9.18 for 0 ° and 7.60 for 10 °) are reached, under observation at an incidence close to normal to the surface.

The test 35 carried out in contrast to the previous one with a relatively small thickness, also shows values of qui which are appreciably greater than those of the examples whose thicknesses are best suited. For the assemblies considered, these values are between 75 and 85 nanometers. The corresponding samples have a value of ç much lower than the limits indicated above as being those beyond which the attenuation is no longer adequately ensured.

The above results sufficiently show that the sub-layers according to the invention meet the objective pursued. Furthermore, the assemblies comprising sublayer and layer are stable in the mechanical, chemical and thermal resistance tests, and do not exhibit any optical defects. In particular, the layers are very transparent.

Similar results are observed when the phosphostannate or borostannate layer according to the invention is used in a set of anti-reflective layers.

Claims

1. Glazing comprising a glass substrate coated with a pyrolytic layer of phosphostannate or borostannate, with an atomic content of phosphorus or boron which is not less than 6%.

2. Glazing according to claim 1, in which the elements Sn and P (B) are in the atomic ratio Sn / P (Sn / B) from 1 to 4.

3. Glazing according to claim 2, in which the elements Sn and P (B) are in the atomic ratio Sn / P (Sn / B) from 1.85 to 2.25.

4. Glazing according to one of the preceding claims, in which the refractive index of the phosphostannate or borostanate layer is between 1.6 and 1.9.

5. Glazing according to one of the preceding claims, in which the constituent elements of the phosphostannate or borostannate layer are respectively in the atomic contents:

Sn 15 to 35% P (B) 6 to 20%

O 42 to 58% Na 6 to 23%.

6. Glazing according to one of the preceding claims, the constituent elements of the phosphostannate or borostannate layer, are respectively in the atomic contents:

Sn 18 to 26% P (B) 9 to 13% O 48 to 52% Na 14 to 20%. 1. Glazing according to one of the preceding claims, in which the thickness of the phosphostanate or borostannate layer has a thickness of between 50 and 110 nanometers.

8. Glazing according to one of the preceding claims, in which the phosphostannate or borostannate layer is arranged as a sublayer of an oxide layer giving the glazing low-emissivity and / or sunscreen properties.

9. Glazing according to claim 8, in which the oxide layer conferring the low-emissivity and / or sunscreen properties is a layer based on tin oxide doped with fluorine. 10. Glazing according to claim 8, in which the oxide layer conferring the low-emissivity and / or sunscreen properties is a tin oxide layer containing antimony oxide, the atomic ratio Sb / Sn being between 0.02 and 0.15. 11. Glazing according to one of claims 1 to 7, in which the phosphostannate or borostannate layer is arranged as an underlayer of a set of anti-reflective layers.

12. Process for the production of a glazing according to one of the preceding claims, in which the phosphostannate layer is formed by pyrolysis from gaseous precursors comprising triethylphosphite (TEP) and monobutyltrichlorétain (MBTC).

13. A method of producing a glazing unit according to claim 12, in which the gaseous precursors also comprise water vapor, the water / MBTC volume ratio being less than 10%. 14. Process for producing a glazing unit according to one of claims 12 or 13, in which the precursors also include air to accelerate the deposition reaction. 1. The process for producing a glazing unit according to one of claims 12 to 14, in which the pyrolysis is carried out at a temperature between 550 and 670 ° C.